Using Spline for Baseline Subtraction (Pro edition only)

You can use cubic spline to fit and subtract baseline on Fit Plot. To create spline curve click on Add button in Fit Curves tab of Fit Plot.

Don't use splines to subtract baselines which can be fit well enough with line curve (line or constant baseline). You can subtract wide peaks by mistake using spline.

Editing Spline

Created spline has 3 anchor points by default. You can move, add and remove anchor points:

Move anchor point with mouse

Double click on spline curve to add new anchor point

Double click on anchor point to remove it

Using spline for baseline fitting

Fitting with Spline

Spline anchor point (x, y) coordinates are treated as fit parameters so you can perform fitting with spline. Note that the anchor point coordinates will be varied but the number of point will remain. You also can lock some parameters (usually x coordinates) by setting Lock check boxes in parameters table.

It is recommended to set appropriate fit intervals which contain only baseline without peaks. In such case Fit One Curve button is more acceptable than Fit by Sum button, because the individual interval for current curve will be used and the interval from Fit Interval tab (which is used to fit by sum of curves) is ignored. Select spline curve and check Set Interval check box in the bottom of the panel to edit spline interval, then click on Fit One Curve button.

Set Baseline check box in spline row in curves table to subtract spline from data.

Setting Fit Interval for spline curve Spline subtraction result